154 PSEUDOCERATITES OF THE CRETACEOUS. 
that of Gerhardtia. This occurs in an earlier age in Carstenia caicedi. 
Descriptions are wholly taken from Karsten’s figures.“ 
CARSTENIA SUBCAICEDI (Karsten). 
C. subcaicedi (Karsten) is described by that author as having heavy 
coarse coste bifureating like those of caicedi and, if his small figure 
represents the young or a primitive dwarfed form of this group, it shows 
how very distinct its development must be as compared with that of other 
genera. 
CARSTENIA? TUBERCULATA 0. sp. Hyatt. 
C.? tuberculata (Pul. provincialis Gerhardt)’ is described by that author 
as identical with lindigi Karsten. It is, however, less involute, and, 
although having similar quadragonal volutions, has costz like those of 
Gerhardtia and there is no median lateral line of tubercles. The sutures 
are more like those of Metoicoceras than of Heinzia provincialis. It is 
possible that the development of this species may show it to be more nearly 
related to Metoicoceras than to Carstenia. It has, however, the peculiar 
channeled bases of the second row of tubercles on either side that have 
been found so far only in this last-named genus. All of these have been 
supposed to be of Barremian age. Its characteristics seem also to ally it 
decidedly with such forms as Heinzia provincialis, and to indicate a common 
origin for all of these genera in some primitive form with similar but more 
tuberculose volutions. It is obviously a more primitive form than Heinzia, 
which has more compressed and often more involute shells and retains in 
its latest stage the form and aspect of the young of H. provincialis and of 
the earlier neanic stage of Metoicoceras swallovi. The resemblances to 
Gerhardtia are also close, as may be seen on Gerhardt’s plates, and its 
form is similar to the young of Carstenia caicedi as figured by Karsten. 
These affinities and its obviously primitive larval characteristics show 
it to be the nearest approach yet found of the probable genetic ancestor of 
the Heinziidee. 
aGéol. de ’ancienne Colomb. Venez. Nouy. Gren. et Ecuador. Berlin, 1886. 
>Kreidef. in Columbien: Neues Jahrbuch ftir Min., Geol., und Pal., Beil.-Bd. XI, 1897-98, p. 152, 
pl. 2, fig. 8. 
